1. Field of the Invention
This invention relates to a tunnel magnetoresistive effective element (hereinafter, often called as a “TMR element”), a thin film magnetic head, a magnetic head device and a magnetic disk drive device.
2. Related Art Statement
With the development of the recording density in hard disks (HDDs), it is required to enhance the sensitivity and the output power in the HDDs. Recently, attention is paid to TMR elements to satisfy the above requirements in the HDDs. The TMR element has a ferromagnetic tunnel film with a multilayered structure of a ferromagnetic layer/a tunnel barrier layer/a ferromagnetic layer. The ferromagnetic tunnel effect is defined as the change of the tunnel current in the tunnel barrier layer depending on the relative angle between both of the ferromagnetic layers when flowing a current between the ferromagnetic layers. In this case, the tunnel barrier layer is composed of such a thin insulating film that electrons can penetrate through the tunnel barrier layer with maintaining their spin conditions.
It is reported that the TMR element has a large resistance change ratio ΔR/R of 12% and over. Then, the TMR elements are expected as next generation sensors to substitute for spin valve film (hereinafter, called as a “SV film”) elements, but they have been just applied for magnetic heads, so that as of now, it is required to make the most use of the TMR elements in the magnetic heads. That is, it is required to design a new magnetic head structure which is not proposed in the past because in using the ferromagnetic tunnel effective film of the TMR element, a current is flown in the stacking direction thereof.
U.S. Pat. Nos. 5,729,410, 5,898,547, 5,898,548 and 5,901,018 disclose conventional magnetic head structures using the TMR elements which are improved in order to realize their super high density recording. However, the requirement for the super high density recording in the TMR magnetic heads are increased, and recently, high-performance TMR magnetic heads are desired.
For example, in using the TMR element as a reading element of a thin film magnetic head, it is very important to design a bias magnetic field means for the free layer. Since a current is flown in a direction perpendicular to the TMR element, that is, the stacking direction, the contact of a hard magnet to the end of the TMR element may cause the short circuit of the TMR element as in a GMR head. As a result, a given current is flown in the tunnel barrier layer and a sufficient output power can be obtained due to the insufficient TMR change ratio.
In order to remove the above matter, U.S. Pat. No. 5,729,410 discloses that a thin insulating layer is provided between the hard magnet and the TMR element for insulation. Moreover, the present inventors have proposed in Japanese Patent Application No.11-171869 that a flux probe portion made of a T-shaped soft magnetic film, of which the base portion is elongated beyond the ferromagnetic tunnel effective film of the TMR element, is provided in the TMR element, and the hard magnet and an antiferromagnetic layer are provided on both edges of the base portion of the flux probe portion.
However, magnetic recording patterns in a magnetic media are reduced with the development of the recording density and thus, it is required to reduce the size of the TMR element to be mounted on a reproducing head. For example, in order to realize a recording density of 40 Gbspi, the TMR element should be reduced to the size of about 0.4×0.4 (μm2), and thus, the hard magnet and the antiferromagnetic films should be reduced. Therefore, if the above prior art technique is applied, it is difficult to apply a sufficient bias magnetic field to the free layer.